In a Long Term Evolution-Advanced system (LTE-A), the reporting of channel state information (CSI) is classified as the periodic CSI reporting and the aperiodic CSI reporting.
The periodic CSI reporting is configured by a higher-layer signaling, i.e., the period and time offset of CSI reporting is configured by a higher-layer signaling, the terminal (UE) transmits the CSI on a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH) of a subframe satisfying the condition according to the period and time offset configured by the higher-layer signaling. For example, assuming the period of CSI reporting configured by the higher-layer signaling is NP, the time offset of CSI reporting is Noffset, the UE transmits CSI on the time slot satisfying the condition (10×nf+└ns/2┘−Noffset)mod(NP)=0, wherein: of is a radio frame number, ns is a time slot number within a radio frame.
FIG. 1 is a schematic diagram of an existing periodic CSI reporting.
As shown in FIG. 1, assuming NP=5, Noffset=2, on radio frame 0, it is calculated according to formula (10×nf+└ns/2┘−Noffset)mod(NP)=0 that the UE will transmit CSI on time slots 4, 5, 14 and 15.
The aperiodic CSI reporting is triggered by the “channel state information request information (CQI Request)” event in the physical downlink control channel (PDCCH) scheduling the PUSCH, the UE transmits aperiodic CSI on the PUSCH depending on the state of the “channel state information request information”.
FIG. 2 is a schematic diagram of an existing aperiodic CSI reporting.
For example, see FIG. 2, if UE receives effective “channel state information request information” that CQI Request bit is equal to 1 carried in the PDCCH scheduling the PUSCH in subframe 4, the UE is instructed to transmit aperiodic CSI on PUSCH on subframe 8.